1. Field of the Invention
The present invention is directed to a non-reciprocal component element for integrated optics which element is particularly useful as an isolator, a directional coupler and/or a modulator for the waves carried in the component.
2. Prior Art
In microwave technology, non-reciprocal component elements are known. For example, a hollow metallic waveguide for the advancing and returning of microwaves is provided with a pre-magnetized ferrite body to form a ferrite phase shifter. A non-reciprocal property of the ferrite shifter influences the propagation constant such that the phase shifts for the advancing and returning electro-magnetic waves are different.
In optical transmission technology, as in microwave technology, non-reciprocal component elements are necessary. Isolators are particularly necessary in the case of optical transmission paths which contain optical amplifiers, such as lasers, in order to prevent the amplification of reflected optical signals and thus to prevent oscillation of the optic amplifiers. Embodiments of the integrated optics for such a component are discussed in the following two articles: John Warner "Faraday Optical Isolator/Gyrator Design in Planar Dielectric Waveguide Form" IEEE Transactions on Microwave Theory and Techniques, Vol. MTT 21, No. 12, December 1973, pp. 769-775, and Shyh Wang et al. "Studies of the Use of Gyrotropic and Anisotropic Materials for Mode Conversion in Thin-Film Optical-Waveguide Applications" Journal of Applied Physics, Vol. 43, No. 4, April 1972 pp. 1861-1875. However, these embodiments have the disadvantage in that they require a phase adaptation between the gyrotropic and the anistropic material over a length of several millimeters.